Dirty Little Secret
by the.eye.does.not.SEE
Summary: An exploration of Mark and Lexie's relationship post-"Teach me." Season 5: What might've happened.


Inspiration: _Dirty Little Secret _by The All-American Rejects (quite a blast from the past, eh?) …Also, I just really love/miss the fifth season.

Rating: M, for some language and sexual themes/content.

Author's Note: For your reading convenience, please note that **none** of these sections directly follows one another. Roughly, they're all spaced a couple weeks, maybe a few months, apart. Please enjoy:

**_._**

**_Let me know that I've done wrong_**

**_When I've known this all along_**

**_I go around a time or two_**

**_Just to waste my time with you_**

_._

Lexie Grey stares down at the small slip of paper in her hand for the fiftieth time today as she lingers outside the exam room door. _Thank god this hallway is empty, _she thinks, grateful, at least, that there's no one to remark on her peculiar hovering behavior. She feels a blush rise to her skin a moment later, realizing that that emptiness factor was probably one of the major factors in him picking this room. She glances down at the note in her hand again.

_I've got a break at five. I'll be in room 223._

She takes a shaky breath, looking back up. She glances to the clock at the wall. 4: 58. _Time to make a decision, _she tells herself, though she knows the decision is already half-made. She's been loitering in the far end of this hallway for the last five minutes. She's looked up and down either side of the hallway about six times a minute, but there's been no sign of him. Unless he's already inside, he's probably on he's on his way here. Expecting her.

She takes a deep breath, puts her hand on the door's handle, closes her eyes, and pushes the door open. She opens them as she steps inside, releasing the large breath she'd been holding in relief—the room's empty. _He isn't here,_ she thinks. _Maybe he's not coming._ She expects relief to flood through her body… But instead, she feels only…disappointment. _It's just because I've built this moment up so much in my head, _she tells herself, remembering how, after she'd found the note, she'd spent almost her entire workday trying to figure out when he'd had time to slip it in her pocket and what she should make of it. _It's not because of him. It's not because of him. It's not because of—_

"Nice of you to join me."

She jumps in place at the voice, her body whirling towards the sound. She hears him laugh when she turns the wrong way, and she immediately whips around, her heart pounding. "You almost gave me a heart attack!" She shouts, her voice reverberating within the empty room. "What the hell are you doing, hiding in the corner!"

Mark Sloan raises his hands in a gesture of peace. "I honestly didn't mean to scare you," he replies, getting up from the chair he'd been sitting in and walking a few paces to the center of the room. He drops his left hand, keeping his right aloft. "Hand to God."

Lexie crosses her arms over her chest, replying, "I have a very hard time believing that you believe in God."

He grins in reply, dropping his hand.

"We…" She exhales, gathering her strength. "We can't do this." Her eyes flick around the room. "Not here."

He frowns. "I thought you'd prefer it to an on-call room. It's more private."

"I don't mean the room," she replies. "I meant—I _mean_—the hospital. We can't do this in the hospital."

"Where do you suggest we do it, then?"

Lexie purses her lips at the suggestive smirk on his face; she knows his phrasing was intentional. "I'm suggesting we _don't_," she replies. "Let's just stop."

She watches as his eyebrows rise in genuine surprise. "'Let's just stop?'" He repeats, taking another step towards her. "I wasn't aware that was an option, Lexie."

Her eyes widen momentarily before they narrow dangerously at him. "I'm going to pretend you didn't just overtly threaten me, Dr. Sloan," she bites out.

The casual, annoyed way he rolls his eyes makes her want to punch him, just for a second. "Oh, you know how I meant it, Grey."

She sighs a moment later, and from the tone of it, they both know she's given up on that particular argument. _It's no use arguing with him anyway,_ she thinks to herself. _He'll win anyway. He always wins. _Her expression grows stormy at the thought. _He. Always. Fucking. Wins._

"What are you thinking about so hard over there?" He smirks, drawing her out of her thoughts. "Me?"

"No," Lexie replies crossly. Her residual anger makes the word come out loud and abrasive—the word is easily pegged for the lie that it is the moment it hits the air. His smirk widens. "This isn't right," she begins a moment later, changing tactics. "This shouldn't be happening between us."

"I won't argue you that," he replies. When he takes another step forward, he draws out the gesture, as if he knows he's taunting her. _Which, _Lexie realizes in annoyance, _he probably does. _"But does it really matter?" His voice is a quiet, almost a whisper. But now that they're standing only two feet away, she can hear it as clearly as if he'd shouted it.

She turns her head away. "Dr. Sloan—"

"Mark," he corrects automatically.

She sighs, closing her eyes for a second before looking up at him. She stares into his oddly familiar blue eyes, blinks a few times, and eventually gives up. _Just like I always do._ "What are we doing?" She asks softly, feeling the resignation wash over her. _Just like it always does._

"We're having a conversation."

"Be serious for a second, please."

"I am serious," he replies with a mocking grin.

Lexie ignores him, looking away as she bites her lip worriedly. "This is the fourth time this week it's happened. The fourth time we've been together."

"So?"

"Four times in one week, I said!"

He smirks. "And yet you're still coming back for more."

She glares at him, lifting a finger to point menacingly in his direction. "Do not blame this on me! I'm not the one slipping notes in people's pockets during rounds!"

"Yours was the only pocket I slipped a note in." He grins. "And I would be glad to proposition you much more publicly, but we both know that isn't really an option right now."

Lexie looks down, her eyebrows knitted together as she chews on her lower lip in worry. "It… It shouldn't just be this…this…"

He frowns. "What should just be 'this?'"

"Us," she replies immediately, before she can stop her mouth from spouting out her thoughts. Her face goes pale white a second later, just before a rosy blush flames out over her cheeks. "There—there _is _an… an 'us,' right? I mean, we're—"

"We're sleeping together, Lexie." He stares at her, and she watches as his gaze tightens. She can feel his judgment on her like a horrible, tangible shadow. It makes her skin crawl, and not in a good way. "Since when are we anything more than that?"

"We—we aren't," she replies quickly. "I just—I meant…" She sighs a second later, giving up again and reaching into her pocket for the small slip of paper. "Notes, Mark? Really?"

"What?" He replies, offense coloring his tone. "What's wrong with the note? I already told you: If you didn't want to come, you didn't have to. It was your choice."

"I know that. It's just that noes are so…" Lexie trails off, searching for the right word. "Childish," she finally settles on, meeting his eyes. When he stares at her in confused disbelief, she continues: "You know, like when you were in the fourth grade and you'd pass a note to a girl… '_I like you, do you like me? Check yes or no._'" She can't help but smile, thinking of him doing just that. "It's childish."

He grins a second later, and from the smooth way it spreads out across his face, Lexie knows he's caught on. And when he steps closer a moment later, she knows he's planning something. So it comes as no surprise when his hand finds its way under her lab coat to cup the small of her back. His fingertips just begin to brush the swell of her buttock as he speaks. "Would it be less childish if the next note said, '_I want to fuck you, do you want to fuck me? Check yes or no'_?"

Lexie can't help but grin, and at the thought of such a thing, a giggle escapes from between her lips. It echoes faintly in the large, empty room. She catches sight of his matching smile just before he bends down and covers her mouth with his, just before they stumble their way to the closest stable surface.

A little under an hour later, when they've finally come down from their highs and gotten to their feet, Mark voices the question they'd both been wondering—but unable to ask—since their secret meetings began.

"Same time tomorrow?"

Lexie bites down on her lip to hide her smile. "Maybe," she replies evasively.

"Come on, Grey," he mutters in quiet exasperation. "Don't play coy with me."

Lexie can't help but smile this time, hearing the amusement in his voice. "Can't help it," she replies, looking down and feeling a blush creep onto her cheek at how easily he spotted her for what she was. "If you haven't noticed, it's kind of the only strategy I have."

"That and ripping off your clothes," Mark replies dryly.

Lexie rolls her eyes, getting up and stretching her legs. She squeezes her eyes shut, yawning and stretching her arms. When she opens them, she almost jumps; he isn't standing more than a foot away. "Y—Yes?" She manages, wondering what he wants.

"You never answered my question," he murmurs slowly. Lexie feels her body heat up as his eyes travel all over her face.

"And what—what question was that, exactly?"

He leans towards her, holding her gaze the whole time as he invades her personal space. "Would you check yes or no, Lex?"

She stares at him in wide-eyed shock for a second before a slow smile makes its way onto her face. "What do you think?" She returns.

"Hm, see, I don't know," he mutters, letting his arms once again encircle her petite waist. "That's why I asked you, Little Grey."

She can't help but smile at the nickname, and even though she knows this thing between them has gone too far already, she leans towards his searching lips. For a minute, as they kiss, she pretends he wants her just as much as she does, and for the same reasons.

"I'd check _yes_," she mumbles against his lips, her arms snaking around his back as her feet shuffle closer. She can feel him smile into the kiss, and all at once, she realizes she isn't ready to let him go just yet, not matter what he does or doesn't feel for her, no matter what this thing between them really is.

.

**_Tell me all that you've thrown away_**

_._

"Are you okay?" He asks, turning his head to stare at the door she just slammed shut.

Lexie's eyes flash to his, and if she weren't infuriated with her job performance after only half of a day, she might stop to appreciate what sounds like concern in his voice. But she's too angry and stressed about having just embarrassed herself during surgery to pay much attention to what he's saying or how he's saying it.

"I'm fine," she replies quickly, not wasting anytime and tugging him towards her. He pulls back automatically, studying her.

"Maybe we should do this later..." Mark suggests.

"Why?" She demands immediately. Her tone sounds insulted to Mark's ears, though he can't understand why. He's only trying to help.

"Because you..." He balks for a second under her uncharacteristically intense gaze. "You seem upset," he finishes finally, feeling oddly unsure of himself. "And…"

"Well, how I feel isn't really your concern, is it, Dr. Sloan?" She snaps, surprising him with the harshness in her voice. "What do you care if I'm upset?" She pauses, and for a second, he's sure she's about to apologize, but instead, she stays silent. Just as he's opening his mouth to question her further, her lips crash against his, so forceful that he's almost bent backwards under the assault.

"Lexie," he tries to cut in as he pulls them slightly apart and stares down at her. "Lex—"

"I said I wasn't your concern, Dr. Sloan." Her tone hardens. "That wasn't a ploy to win your sympathy. It wasn't a tease to get you interested in my emotional life. It was the truth. We're sleeping together; that does not mean we're dating. I'm not asking you to care about me, I'm asking you to fuck me. So, come on," she says, jutting her chin out at him. "Let's go. I have a half hour and a hell of a lot of stress to relieve."

He stares at her for a moment, unsure of what to say, but in less than a second, she's pulling him toward her so rapidly, and kissing him so fiercely, Mark's sure his head would be spinning... If only it wasn't already.

_._

**_Find out games you don't wanna play_**

**_You are the only one that needs to know…_**

_._

"I… I'm not so sure about this."

"What?" He asks in a whisper. He sweeps her hair away with a hand, exposing her neck to him. She shivers slightly when she feels his warm breath on her neck, soon followed by his lips. "What aren't you sure about, Lex?" He murmurs against her skin.

"We're—in your office."

"Exactly. Privacy. More than an on-call room, more than an exam room…" He presses a deep kiss against her neck. "We can lock the door and be in here as long as we want. No interruptions."

Lexie feels her eyes fall closed and her body shiver against her will at his words. She's giving herself away—laying her need for him right out in the open—and yet she can't find it in herself to care. Not right now, at least. Her breathing picks up as his hands move to the center of her body—drifting from merely cupping her waist lightly to—

"_Mark_." She gasps his name, her hips bucking forward as his hand slips under her scrubs, her underwear, inside—

"You still unsure?"

His chin hovers by the curve of her shoulder, and the stubble on his cheek scrapes against her smooth skin; a tingling contrast to his soft voice.

She can barely manage a soft moan in reply.

"Are you still unsure, Lex?" He asks again, enunciating each word perfectly; his hard voice demands an answer.

"You're—compromising my judgment," she manages to say, shuddering as his figures continue to explore her wet folds.

"I was wondering when you'd finally admit it."

She can hear a laugh in his voice, and it's that carefree sound that makes her spin around. She wishes her head cleared the moment he was no longer touching her, but, of course, that is not the case. The sight of him, the scent of him, the fact that he's close enough to _touch_… Lexie grins, tipping her chin over his shoulder. He steps to the side, following her gaze.

"Why, doctor…" She smiles to herself, taking his hand and pulling him along after her as she takes a few steps forward. "Your desk looks awfully clean…" She sighs dramatically, pressing her chest against his.

A smirk spreads slowly over Mark's face as he takes in the suggestion behind her words. "You wanna dirty it up?" He wonders, running his hands over the smooth curves of her waist and butt as he looks at the piece of furniture in question.

His desk is, in fact, a mess. There are stacks of paper covering almost every inch of the polished wood. Case files are stacked so high that they're almost as tall as the young intern standing before him. An endless showering of prescription sheets hovers in a light film above all the paperwork, precariously holding their positions as they rest just above their assigned cases, not yet attached.

With one quick sweep of his arm, he shoves all of that to the floor. He'll spend hours picking it up and sorting through it all again later, he knows, but right now, it doesn't matter one bit. All that matters is her. Being with her. Pleasing her.

Making sure she'll come back.

And from the naughty smile lighting up her face as she lies back on his now-clean desk, he's almost one hundred percent sure she'll be back. _But just in case… _He tears off his shirt, tossing it among the strewn papers on the floor, and bends low over her to cover her body entirely with his. He does his best, just in case, and as if right on cue, she's moaning in less than twenty seconds, panting in mere minutes, and—he knows—she'll be screaming all too soon. _That's the only downside, _he thinks, closing his eyes and slipping his hands underneath her shirt as she wraps her legs tight around his waist, _this room isn't soundproof._

_._

**_Who has to know?_**

**_When we live such fragile lives,_**

**_It's the best way we survive_**

**_I go around a time or two_**

**_Just to waste my time with you_**

**_._**

Mark opens the door after hearing a quiet knock. He stands back, letting the door swing open to reveal Lexie Grey. She stares at him for a moment before smiling in wordless chagrin and shrugging, as if that will explain her presence at his doorstep.

"I guess I'm not ready to call this off just yet." She watches for his reaction while hitching her purse higher on her shoulder, as if she's preparing to leave. As if she thinks he'd be stupid enough to send her away. "What about you?"

"I wasn't the one who called it off," he replies, his voice only a few degrees above freezing. He stares at her, remembering how she'd laid down the ultimatum just two weeks ago: _either tell Derek or we're done_. He hasn't seen her since. That sad, dour meeting in the on-call room was the last time he'd had contact with her. And every day since then, he's wanted nothing else than to pull her aside, to find a moment alone, to _explain_…

They stare at each other for a long, tense moment before Mark steps forward, taking her unsuspecting face in his hands and kissing her hard on the mouth. Lexie staggers back in surprise for a brief moment before righting herself and lurching back towards him, her lips just as desperate for his.

They break apart only when the need for air becomes so great that they're both panting.

"What about telling them?" Mark manages to ask, wanting to set the record straight, not wanting this night to be simply fulfilling a desperate, bodily whim. "You wanted me to—"

Lexie shakes her head. "No. Forget about them."

"_Lexie_," Mark stresses seriously, "you said you wanted—"

"Forget what I said," she cuts in, her tone matching his. It falls a second later, and when she speaks next, her voice is soft and hushed. "I only want you," she murmurs, looking to the floor.

He tilts her chin up to meet his with a few fingertips. "Hey. You mean that?"

She nods, her intense dark brown eyes trained on his. "Yeah," she whispers, her voice barely audible. "I do."

He can hear the fear in her voice. It cracks her words, averts her eyes, and makes her jumpy. He can hear it, and he doesn't want to. He doesn't want to worry her, he doesn't want to hurt her, he doesn't want to make things any harder…

He drops his hand from her face; it seeks out hers blindly. "Wanna come inside?"

She nods shallowly, never letting her gaze waver. She steps forward to enter, but before she can cross the threshold, he tugs her arm, pulling her tight against him. Her breath escapes her in a tiny gasp and her eyes are large and wide as they stare up at him.

"I don't want you to worry anymore, okay? We'll figure this out."

She nods again, more convincingly this time. She doesn't move to shake off his hand or step out of his embrace. Without a word, their lips meet again, more passionate and intense than the last. They both have something to prove here, tonight, and neither plans on resting until the other understands.

**_._**

**_Who has to know?_**

**_The way she feels inside…_**

**_Those thoughts I can't deny…_**

**_These sleeping dogs won't lie_**

**_._**

"Where are you going?" He murmurs, blinking back from his dozing to find her half-clothed and hunched over her shoes.

"Back home," she replies quietly. She stares at him for a moment before turning away and pulling her shirt on. "I have—"

"Stay."

She looks over, feeling her heartbeat pick up double-time as she sees his hand spread out across the bed towards her. "What?" She whispers a moment later.

"Stay," he repeats. "Whatever you have to do, it can wait a day."

"Mark, I… I have to go home." She gives him a weak smile. "Meredith needs to see that I'm alive, and I need to sleep, and I'm not really up for another round—"

"I didn't mean you had to stay for that. I just meant…" He glances away from her, to the foot of the bed. "You can stay," he finishes finally, his eyes settling on her once again. "You don't have to keep running out."

"But I thought we weren't…" Lexie swallows. "I thought we weren't an… 'us.'"

"Does you sleeping here make us an 'us?'" Mark asks.

"Does it?" Lexie counters.

Mark sighs, looking down again. Lexie watches, waiting for his blue eyes to find hers again, but they don't lift from their downturned angle. "I'd just… I'd like it if you stayed."

Lexie makes herself take a calming breath before speaking again. She hopes her voice sounds normal despite the banging in her chest. "You would?"

"You know what?" Mark asks, his eyes flying to hers as his voice takes on a steely edge. "You want to go? Fine. Go. I was just offering—"

"No, no, no," Lexie cuts in. "No, I'll stay." She swallows nervously; the hard set of his eyes and mouth hasn't melted from his features yet. "If you want me to, that is," she adds quickly.

He nods stiffly, staring at her for a moment before pushing himself up against the pillows. "You can stay," he replies, turning away and busying himself with something on the nightstand. Lexie stares at him for a long moment, and when he doesn't roll back over to meet her eyes, she gets the odd impression that he's embarrassed. _For how he acted or for what he said? _She wonders. _Or because of me?_

But a few seconds later, all those thoughts fly out the window.

"I brought you these," he explains, holding out a pair of sky-blue scrubs, "so if you want to stay some nights…" His eyes rise slowly to meet hers. She hopes the shock on her face doesn't scare him away. "This way you won't need to make up a story or struggle through an explanation. Just say you spent the night at the hospital."

"I…" Lexie licks her lips, trying to get her mouth and brain to work in tandem. Shakily, she reaches out for the clothing. She glances down at the pants and shirt as she gathers her thoughts. _They're my size, _she observes, staring at the tags. _He actually went through the trouble to find my size._

"Thank you," she finally settles on, looking back up as she clutches the blue fabric between her fingers. "That was… really considerate of you."

A smile flickers on his lips, but it's not quite one she can read. There's no suggestion, no innuendo, no mocking or amusement... He just looks kind of…happy.

"Yeah, well," he shrugs, as if to downplay the gesture. "I figured that if I was going to ask you to stay here, I might as well provide some amenities."

"Well, that was, uh, really…" _Sweet. Nice. _"It was really good of you," she finishes, knowing the other options would make him wrinkle his nose in disgust. She's half-worried about what his response to this one will be, too, considering how much they'd debated the morality of their relationship.

Yet all she sees is that smile again. That happy smile.

She smiles back, unembarrassed when the gesture spreads wide over her face. She hopes he can tell that she's happy too.

**.**

**_I'll keep you my dirty little secret_**

**_Don't tell anyone or you'll be just another regret_**

**_I'll keep you my dirty little secret_**

**_Who has to know?_**

**_._**

"Come with me," she whispers, grabbing his hand.

"Wha—"

"Come here," she hisses with a smile, pulling him down the hall towards the nearest on-call room.

"Are you going to tell me what we're doing?" Mark wonders, letting himself be herded into the dark, empty room.

"I think you know exactly what we're doing," she replies, closing the door behind them. Barely a second passes before she's covered his lips with hers, pushing him back against the wooden door with a passionate kiss.

"Easy, Lex," he mumbles amidst her fierce kisses. "Give a guy a chance to catch up."

Lexie chuckles, nipping on his lower lip lightly before pulling back. He can see her wide smile even in the darkness. "You told Derek, didn't you?" She whispers, pressing her hips against his.

He smiles down at her, leaning forward to press a light kiss on her lips. His hands move to cup her face a moment later, angling her eyes to meet his. "I did," he murmurs.

Lexie's eyes search his face in quiet wonder. "Thank you," she whispers reverently, pressing her lips hard against his again. "Thank you so much."

Mark smiles into the kisses, stepping forward so he's no longer trapped against the door. He bends down a second later, scooping her into his arms. "I know your intent is for a quickie here," he smiles, making his way to the nearest cot, "but you better give me a _real _thank-you when we get home."

Her returning laughter makes him grin. "Depends," she replies, "how bad was it, _really_?"

"Not too bad," he murmurs, laying her gently down on the bed. A contended smile graces her face as she stares up at him. He removes his shirt and scrub pants before joining her on the small bed. "He ridiculed me for a bit, mentioned how young you were…" Lexie rolls her eyes. "But mostly," Mark tells her, "he kept wondering why it 'took so long' for me to come forward about us."

Lexie frowns, linking her fingers around the back of his neck. "What's that supposed to mean?"

"That's what I said," Mark replies, running his hands up her sides beneath her scrub top. "And he told me…" He stills his hands, and her eyes find his in the darkness. "That he's known for weeks."

"_Weeks_?" Lexie repeats, her eyes widening in disbelief. "What—What does that mean?"

Mark chuckles, "It means," he begins, pushing her shirt up and pressing soft kisses against her smooth abdomen, "that we apparently weren't as secretive as we thought we were."

"When did he find out?"

"Sometime during those couple months where you spent almost every night at my hotel," Mark replies.

Lexie can't help but smile. "I knew it." She shakes her head, and he glances up at her, wondering. She catches his eye, reaching down to run her hand through his hair. "I knew we'd be found out. We were too caught up in each other to take notice of everyone else, of how we were affecting other people."

Mark grins. "No, no, the front desk did inform me of a couple noise complaints."

"You know what I mean," Lexie smiles, a light blush covering her cheeks at his all-too-true statement.

"I do," Mark replies softly. He presses one last kiss to her navel before crawling forward and pressing his body flush against hers. "And you were right," he agrees as his hands cradle her face gently, "we really were too busy paying attention to each other to keep an eye out. Derek said he saw us go off together three separate times, and that was just in one month."

Lexie smiles, kissing him. "Wow, so he missed the other twenty-seven?" She grins. "What can I say? You were hard to ignore."

"Right back at cha."

"And an even harder secret to keep."

Mark smiles down at her. "You happy, then? Not to be keeping this a secret anymore?"

"Really happy," Lexie replies. She arches her back, bringing her lips in contact with his. "Now how about that quickie? I've got twenty minutes before surgery."

Mark frowns slightly when she catches his eye. "You could've given me a _bit _more time to work with, Grey."

Lexie smiles, threading her fingers in his hair. "Well, that's what tonight is for," she replies. "I'm all yours tonight."

"You're all mine every night," he counters with a smug smirk.

"I know," Lexie grins, holding him close. "And that's the way I like it."

.

_Author's Note: Thank you for reading! Reviews, as always, are **greatly **appreciated!_


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